1. Field of the Invention
The present invention relates to a clamping apparatus and more particularly to a clamping apparatus of the type that pulls a driven rod through a plurality of transmission members by an annular driving member.
2. Explanation of Related Art
A conventional example of the clamping apparatus of this type is recited in Japanese Patent Public Disclosure No. 9-285925 proposed earlier by the Assignee of the present invention. The conventional example is constructed as follows.
A driven rod is inserted into a tubular bore of a sleeve. The driven rod has one end portion provided with an input portion in the shape of a short column. A plurality of transmission balls are inserted into the other end portion of a peripheral wall of the sleeve and spaced apart from each other peripherally at a predetermined interval outside the other end of the input portion. These transmission balls are radially movable. When clamping, an operation cam externally fitted onto the sleeve moves the transmission balls radially inwards to make them engage with the input portion. The sleeve pulls the driven rod toward the one end through the transmission balls.
The conventional technique is excellent in that the operation cam can smoothly and reliably switch over the transmission balls to an engageable position. However, each of the transmission balls is brought into contact with the input portion almost as it makes a point contact therewith to result in limiting a transmission force. Therefore, it still has to be improved for strongly pulling the driven rod.
The present invention has an object to provide a clamping apparatus which exerts a strong pulling force.
In order to accomplish the above-mentioned object, the present invention has constructed a clamping apparatus in the following manner, for example, as shown in FIGS. 1 to 5.
An annular driving member 11 is axially movably inserted into a housing 4. The driving member 11 has a tubular bore 11a into which a driven rod 6 is inserted. The driven rod 6 is provided, at a portion near one end, with an input portion 6a. A plurality of transmission members 15 are arranged peripherally side by side around the input portion 6a. Each of the transmission members 15 is provided, at a portion close to the other end, with an engaging portion 17 which engages with the input portion 6a. The transmission members 15 can switch over between an engageable position (X) where the engaging portions 17 axially face the input portion 6a when the transmission members 15 swing radially inwards and a disengaging position (Y) where the facing is cancelled when they swing radially outwards. The transmission members 15 at the engageable position (X) are movable toward the one end by the driving member 11. The transmission members 15 swing from the disengaging position (Y) to the engageable position (X) by a first actuation means 26 and they swing from the engageable position (X) to the disengaging position (Y) by a second actuation means 32.
The present invention operates in the following manner, for example, as shown in FIGS. 2 to 4.
Under an unclamping condition shown in FIG. 2, the driving member 11 moves downwards, namely in a direction to the other end. The respective transmission members 15 switch over to the radially outward disengaging position (Y) by the second actuation means 32.
When driving the driven rod 6 for clamping, first, as shown in FIG. 3, the first actuation means 26 swings the transmission members 15 to the radially inward engageable position (X). This allows the engaging portions 17 provided in the transmission members 15 to face the input portion 6a from below. Subsequently, as shown in FIG. 4, the driving member 11 drives the transmission members 15 at the engageable position (X) upwards. This enables the engaging portion 17 of every transmission member 15 to push the input portion 6a upwards with the result of strongly pulling the driven rod 6 upwards.
The driven rod 6 is driven for unclamping by procedures substantially opposite to the above ones.
In consequence, the present invention offers the following advantages.
The plurality of transmission members are peripherally arranged side by side around the input portion of the driven rod. They swing radially inwards and then switch over to the engageable position. This allows the engaging portions of these transmission members to face the input portion so that they can make surface contact over substantially the whole periphery of the input portion. Accordingly, these transmission members can strongly pull the driven rod to result in the possibility of providing a strong clamping apparatus.
Besides, the transmission members swing so as to switch over between the engageable position and the disengaging position. This can reduce the strokes for engagement and disengagement of the first and the second actuation means in correspondence with a lever ratio for swinging the transmission members with the result of being able to make the clamping apparatus compact.
Further, the transmission members are arranged around the input portion of the driven rod. This can make the input portion and the transmission members axially overlap with each other. Therefore, the entire length of the housing can be shortened by an amount corresponding to the overlap to result in the possibility of making the clamping apparatus more compact.
The present invention includes the following clamping apparatus.
Each of the transmission members 15 has a portion near one end, which is provided on its outer peripheral portion with a fulcrum portion 16 swingably supported by the housing 4 and has another portion close to the other end, which is provided on its outer peripheral portion with a first portion 18 to be actuated for engagement. The first actuation means 26 is connected to the first portion 18. The portion near one end of every transmission member 15 is provided on its inner peripheral portion with a second portion 19 to be actuated for disengagement. The second actuation means 32 is connected to the second portion 19.
The above-mentioned invention positions the first portion to be actuated and the second portion to be actuated, radially eccentric from each other. This prevents the first and the second actuation means from being arranged in series axially to result in the possibility of reducing the axial length of the clamping apparatus.
The present invention furthermore includes the following clamping apparatus.
The second actuation means 32 comprises a push member 30 which is brought into contact with the second portions 19 of the transmission members 15, and a resilient member 31 which pushes the push member 30 toward the other end. This invention can make the second actuation means simple and compact to result in greatly downsizing the clamping apparatus.
The present invention still more includes the following clamping apparatus.
The driving member 11 comprises a fluid pressure piston. A fluid pressure actuation chamber 12 is formed between the driving member 11 and the other end wall 4a of the housing 4. Further, a return spring 13 is attached between the driving member 11 and one end wall 4b of the housing 4. The first actuation means 26 is provided with a slant cam 27 connected to the driving member 11. This invention can drive both of the driving member and the slant cam through pressurized fluid of the fluid pressure actuation chamber with the result of being able to form the clamping apparatus into a simple structure.